Get User’s First and Last Name in WordPress

The function below can be used to get a user’s first and last name with a space between them, like “Kellen Mace”. If they only have a first name saved, it will return that, and it will return their WP login as a last resort. This is useful if you want to display the users’ names in a list, for example.

/**
 * Get user's first and last name, else just their first name, else their
 * display name. Defalts to the current user if $user_id is not provided.
 *
 * @param  mixed  $user_id The user ID or object. Default is current user.
 * @return string          The user's name.
 */
function km_get_users_name( $user_id = null ) {
	$user_info = $user_id ? new WP_User( $user_id ) : wp_get_current_user();

	if ( $user_info->first_name ) {

		if ( $user_info->last_name ) {
			return $user_info->first_name . ' ' . $user_info->last_name;
		}

		return $user_info->first_name;
	}

	return $user_info->display_name;
}